ARS | Publication request: LABORATORY AND FIELD COMPARISONS OF STRAINS OF BACILLUS THURINGIENSIS FOR ACTIVITY AGAINST LEPIDOPTERAN LARVAE USING GRANULAR FORMULATIONS

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 1997
Publication Date: N/A

Interpretive Summary: Bacillus thuringiensis (Bt) is a bacteria used for contolling agricultural and aquatic pests and is of interest to a range of scientists and public pest control operators. Many strains of Bt have been discovered that have varying levels of activity and host ranges. The purpose of this international, cooperative study was to determine the activity in laboratory and field tests of Bt strains from Mexico and the U.S. Laboratory tests demonstrated that strains from both countries are effective and new methods for fermentation and formulation are acceptable for mass production. Field tests on insects infesting corn also demonstrated good activity, comparable with chemical pesticides. The significance of these findings is that strains of Bt with novel activities can be found in Mexico and that a new formulation, based on corn flour, is effective for delivery of active ingredient.

Technical Abstract: The toxicity of six strains of Bacillus thuringiensis representing four serovars, aizawai, galleriae, kurstaki, and kumamotoensis, were evaluated in laboratory and field studies for activity against three lepidopteran pests, Heliothis virescens, Spodoptera exigua, and Trichoplusia ni. A gelatinized corn flour-based formulation was also evaluated. Results of laboratory tests showed that some of the B. thuringiensis strains isolated from Mexico were sufficiently toxic to warrant further investigation as potential bioinsecticides for lepidopteran control. Nixtamalized corn flour was used to create a granule formulation which remained toxic for at least two years. Field tests were conducted in 1994 and 1995 on corn plots in a semi arid region in central Mexico. In both years, yields from plots treated with several new strains were as high or higher than a commercial B. thuringiensis product or a chemical pesticide. These data suggest that the product can be produced and retain shelf-life suitable for commercialization.